We have developed a radiation resistant bacterium for the treatment of mixed radioactive wastes containing ionic mercury. The high cost of remediating radioactive waste sites from nuclear weapons production has stimulated the development of bioremediation strategies using Deinococcus radiodurans, the most radiation resistant organism known. As a frequent constituent of these sites is the highly toxic ionic mercury (Hg) (II), we have generated several D. radiodurans strains expressing the cloned Hg (II) resistance gene (merA) from Escherichia coli strain BL308. We designed four different expression vectors for this purpose, and compared the relative advantages of each. The strains were shown to grow in the presence of both radiation and ionic mercury at concentrations well above those found in radioactive waste sites, and to effectively reduce Hg (II) to the less toxic volatile elemental mercury. We also demonstrated that different gene clusters could be used to engineer D. radiodurans for treatment of mixed radioactive wastes by developing a strain to detoxify both mercury and toluene. These expression systems could provide models to guide future D. radiodurans engineering efforts aimed at integrating several remediation functions into a single host.
Bibliographical noteFunding Information:
This research was largely funded by grant DE-FG02-97ER62492 from the Natural and Accelerated Bioremediation Research program, Office of Biological and Environmental Research, DOE. Some of this work was also supported by the grant DE-FG07-97ER20293 and DE-FG02-98ER62583 from the DOE; and grant MDA-905-97-Z-0053 from the U.S. Department of Defense.
- Mercuric reductase